Metallic peroxide compounds have been formulated for the purpose of releasing oxygen in situ to support biodegradation of contaminants. U.S. Pat. No. 5,264,018 issued Nov. 23, 1993 to Koenigsberg, et al. describes the use of magnesium peroxide in soils as an oxygen releasing compound. Such material is described in (U.S. Pat. No. 5,395,419 issued Jan. 14, 1993 to Koenigsberg, et al.) as being an oxygen liberating compound for the enhancement of aerobic microbes in the biodegradation of waste materials and as a Therapeutic and Preventative Treatment of Anaerobic Plant and Soil Conditions.
FMC Corporation has sold a product trademarked "Permeox" which includes Calcium Peroxide. This product is marketed as an "oxygen source" for bioremediation. FMC points out in their literature that the intermediate step for oxygen generation is the formation of hydrogen peroxide. This reaction is as follows: EQU CaO.sub.2 +2H.sub.2 0Ca(OH).sub.2 +H.sub.2 0.sub.2
The second stage of the reaction which liberates molecular oxygen is as follows: EQU 2H.sub.2 0.sub.2 O.sub.2 +2H.sub.2 0
Numerous papers have been written on the benefits of using oxygen releasing materials on aerobic bacterial degradation processes. Examples of these are: Jane L. Vernalia, 1977, "Bioremediation of Pentachlorophenol in Soil Under Anaerobic and Aerobic Conditions" ORC Oracle, vol. 1, no. 4; Michael A. Heitkamp, 1997, "Effects of Oxygen-Releasing Materials on Aerobic Bacterial degradation Processes", Bioremediation Journal I (2):105-114 (1997); Bianchi-Mosquera, G. C., R. M. Allen-King, and D. M. Mackay, 1994, "Enhanced Degradation of Dissolved Benzene and Toluene Using a Solid Oxygen-releasing Compound" Ground Water Monitoring Rem. 14 (1):120-128; and Vesper, S. J., L. C. Jurdoch, S. Hayes, and W. J. Davis-Hoover, 1994, "Solid Oxygen Source for Bioremediation in Subsurface Soils", J. Hazard Materials, 36:265-274.
The use of hydrogen peroxide with iron as a co-reagent, was first reported by the English chemist, Dr. H. J. H. Fenton in 1894. Research has been conducted and reported describing Fenton's chemistry which is based on the production of the hydroxyl and perhydroxyl radicals from hydrogen peroxide. See for example: Richard J. Watts, Matthew D. Udell, and Robert M. Monsen, 1992, "Use of Iron Minerals in Optimizing the Peroxide Treatment of Contaminated Soils", Water Environment Research, 65(7):839-844 and Richard J. Bigda, 1996, "Fentons Chemistry: An Effective Advanced Oxidation Process", Environmental Technology. May-June 1996:34-39. These highly reactive compounds rapidly oxidize carbonaceous materials.
However, hydrogen peroxide is relatively unstable, potentially unsafe and typically does not survive in the subsurface long enough to be effective or practical as either an oxygen supplement or as an oxidizing reagent. In addition, the technical difficulties involved in delivering hydrogen peroxide to the contaminated media have limited its use. Hydrogen peroxide is also toxic to microorganisms in higher concentrations.
It has been reported by Bryan W. Tyre, Richard J. Watts, and Glen C. Miller, 1991, "Treatment of Four Biorefractory Contaminants in Soils Using Catalyzed Hydrogen Peroxide", J. of Environmental Quality 20:832-838, that bio-refractory organic pollutants such as chlorinated compounds can be oxidized using catalyzed hydrogen peroxide (Fenton's reagent). These materials, along with certain hydrocarbons, present a challenge to biodegradation because of the lack of reactive sites on the molecules.
Traditional remedial technologies such as a simple pumping and treating of groundwater, vacuum extraction of volatile organic compounds, thermal treatment of contaminated soil or excavation and landfilling of contaminated soil are typically costly, disruptive to normal site activities and may only transfer contaminants to another location or convert them to another form.
While these techniques and systems have advantages in some circumstances, they all suffer from economical, technical or time drawbacks. That is, they are either quite expensive to carry out and disruptive of the site, or they are technically limited by the site hydrology and the nature of the contaminant, or they take a very long time to be effective. There thus exists a need for an economical method that is less disruptive to site activities, less restricted by site hydrology, contaminant type and concentration and still achieve substantial results within a reasonable period of time.
Although in situ bioremediation is becoming increasingly popular as a remedial technology, this process is typically slow and may be inhibited by high contaminant concentrations or the presence of free phase contaminants. In addition, many organic contaminants are biorefractory and, therefore, resistant to biodegradation. The technical difficulties involved in delivering nutrients and oxygen supplements such as metallic peroxide into the subsurface media has also restricted the effectiveness of in situ bioremediation.